The encapsulation or immobilization of proteins, enzymes, antibodies, and even whole cells within silica gels is an exciting new area of materials research which has been made possible by the use of the sol-gel method, wherein proteins are entrapped within the silica network under conditions which preserve the structure and function of the molecule. These novel composite materials are potentially useful as biosensors, electrodes, immunodiagnostics, and optical components. Silica gel is also a potential bone substitute material which has recently been demonstrated to induce apatite formation in in vitro and in vivo tests. However, the rate of apatite induction on silica gel is slower compared to other bioactive materials, which may ultimately delay or even prevent tissue bonding. Therefore, it is of interest to explore ways of accelerating the apatite induction rate on silica gel. The applicant hypothesizes that it is possible to accelerate apatite induction on silica gel by immobilizing apatite-nucleating macromolecules within the structure of the gel. This will be accomplished by encapsulating acidic proteins using sol-gel processing. Sol-gel processing parameters will be systematically studied to define the optimum conditions for protein encapsulation, and to determine the effect of processing conditions on protein structure and bioactivity. The secondary structure of encapsulated protein will be monitored using circular dichroism spectroscopy, and an in vitro simulated body fluid assay will be used to monitor apatite induction. Knowledge of the structural state of encapsulated protein will allow us to determine the effect of protein secondary structure on apatite induction. By exploring new approaches to enhancing apatite induction on inorganic materials, the proposed research may lead to new bioactive materials based on silica gel, as well as improvements in the apatite induction rate on existing bioactive materials. In a broader context, this research will increase significantly our understanding of the effect of sol-gel processing conditions on the structure and activity of encapsulated proteins, which will be useful as this line of research expands to include naturally derived osteogenic proteins and other sol-gel matrices such as titania gel.
